Tissue Distribution of [¹⁴C]-Lefamulin into the Urogenital Tract in Rats

Area of Science:

• Pharmacology and Toxicology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Lefamulin is an approved antibiotic for community-acquired bacterial pneumonia.
• It exhibits potent in vitro activity against key sexually transmitted infection (STI) pathogens, including multidrug-resistant strains.
• Understanding drug distribution in urogenital tissues is crucial for evaluating its potential in STI treatment.

Purpose of the Study:

• To investigate the tissue distribution of lefamulin in the urogenital tract of male and female rats.
• To assess lefamulin distribution at a cellular level using advanced autoradiography techniques.
• To determine the potential of lefamulin for treating STIs based on its pharmacokinetic profile in relevant tissues.

Main Methods:

• A nonclinical study utilizing quantitative whole-body autoradiography (QWBA) and tape-transfer microautoradiography (MARG).
• Administration of a single intravenous dose of [14C]-lefamulin (30 mg/kg) to male and female Sprague-Dawley rats.
• Analysis of tissue distribution at 0.5, 6, and 24 hours post-dose.

Main Results:

• Lefamulin demonstrated widespread distribution throughout rat carcasses, with high concentrations in urogenital tissues.
• Specific areas of high concentration included the male bulbourethral gland, urethra, prostate, and female clitoral gland, uterus, and ovary.
• Concentrations in these tissues were comparable to or exceeded those in the lungs, peaking at 0.5 hours and remaining detectable up to 24 hours.

Conclusions:

• Lefamulin exhibits rapid and homogeneous distribution into urogenital tissues down to the cellular level in rats.
• High tissue:blood ratios were observed in key urogenital areas relevant to STI treatment.
• These findings support further investigation of lefamulin for potential clinical evaluation in STI treatment.